#include <bits/stdc++.h>

using namespace std;
long factorial(int x)
{  long fact;
    if(x==1 || x==0)
      fact=1;
     else
     {   fact=1;
        for(int i=1;i<=x;i++)
        {
        fact=fact*i;
        }   
     }
  return fact;
}
long countArray(int n, int k, int x) {
   long result;
     if(k>(n-2))
         result= (factorial(k)/factorial(k+2-n))-3;
     else 
         result=(factorial(n-2)/factorial(n-2-k))-3;
    return result;// Return the number of ways to fill in the array.
}

int main() {
    int n;
    int k;
    int x;
    cin >> n >> k >> x;
    long answer = countArray(n, k, x);
    cout << answer << endl;
    return 0;
}